The present invention relates to methods for the renovation or adaptation of refractory valve plates used in slide gate valves for casing ladles or tundishes for controlling molten metal pouring.
Various methods are known for repairing valve plates, according to which there are inserted into the bores of the worn plates annular parts which have exactly the same thickness as the plates themselves. For valve plates having an integral "nose" or nozzle, it is known for the bore in the latter to be filled with a cement-like filling compound.
Ring-shaped inserts which have been used in prior art methods have comprised two cylindrical portions having different outside diameters, the portion having the larger outside diameter being the upper part of the ring insert.
The known prior art methods have disadvantages, the most serious of which will be now mentioned. Firstly, the ring insert for a stationary plate can extend downwardly therefrom and press on the movable plate. Secondly, the upper part of the ring insert for the stationary plate is very frequently oversized, so that the periphery of the ring insert is undesirably close to the annular recess provided, in the upper surface of the stationary plate, for sealing engagement with a refractory discharge outlet member of the associated pouring vessel. This results in the plate area between the new ring insert and the recess being considerably reduced, which may lead to leakage of molten metal.
For the movable plates, the disadvantage of a ring-shaped insert having a length equal to the plate thickness consists in that the flowing metal can seep between the lower end of the ring insert and the abutting face of the cement lining of the "nose", and thus along the contact surface between the plate and the "nose". Such may happen particularly when metal is tapped under throttling conditions with the valve only partly open, when the metal flow will possess a horizontal flow component.
The cementitious compound used for the lining of the "nose" of the movable plate is a refractory material, whose poor elasticity may lead to crack formation in the surface as well as in the body of the lining.
Valve plate repair techniques disclosed herein can equally well be employed for adapting conventional valve plates to suit them for use with special steels which may give rise to difficulties when pouring through conventional valve plates.